SLEEKNESS AND COMFORT

Pat Horwitz and her husband threw a penthouse party when this colorful room was finished last year.

But guests didn`t go up to a rooftop room to indulge in champagne and food under the stars. Instead, they traipsed downstairs to the room most commonly known through the years as, forgive the expression, the basement.

''I wanted a strong environment; I wanted to feel like I was going into a completely different room . . . into my penthouse,'' Pat says.

The Horwitzes have lived in their home for 33 years, and the basement (in its prepenthouse days) had been used as a place where their four kids could jump around on old furniture without fear of messing things up. But the children turned into adults, and Pat, teacher and writer, decided she wanted a room where she could work, entertain and be comfortable.

She teamed up with interior designer Vassa, who has a showroom at the Merchandise Mart, to create a room that would be both high tech and comfortable.

''The rest of the house I guess you would call traditional, but I wanted high tech down here,'' she says. ''I think I`m a high-tech type of person. You know, a high-tech person is someone who feels like they`re high on caffeine all the time.''

The colors are basically red, gray, black and white, and the furnishings combine a touch of whimsy (as in the curvy arms of the easy chairs) with sleekness and comfort.

The chairs are all hydraulic. Push one lever, and the back can be adjusted; push another lever, and the chair will go up or down. The light that hangs over a circular glass table resembles a spaceship poised to land and is reflected in an 18-inch-high strip of mirror that stretches along one wall. Another light hangs over the desk like a piece of gently folded paper.

The room is basically divided into two sections. The larger part, on a free-form, raised ceramic-tile platform, is Pat`s working area with a custom- designed, half-circle desk and a 5-foot-diameter table that doubles for conferences and informal meals. There`s no clutter: The desk legs are designed to house electrical wires, and the computer is concealed in the cabinets behind the desk.

A step down from the platform onto the gray Berber carpet is the

''comfort'' part of the penthouse. A dark-gray leather sofa, coffee table and chairs with the wavy arms are grouped around the fireplace and lit by pendant-mounted quartz lights.

A guest would probably remark on the wooden Dalmatian.

''That`s Ginger,'' Pat says matter-of-factly. ''He requires little care. You don`t have to take him outside, which can be such a nuisance in cold weather. But when it is chilly, I have this little coat for him,'' and she drapes a small bright red shawl over Ginger`s speckled back.

The Horwitzes consider the room finished; Vassa wants to see more art on the walls. ''I`m going to keep after her. I`ll keep sending her things,''